1. Field of the Invention
The present invention relates to a composite LC resonator including a plurality of inductors and a plurality of capacitors and to a band pass filter including a plurality of composite LC resonators.
2. Description of the Related Art
A multilayer band pass filter is disclosed in Japanese Unexamined Patent Application Publication No. 2011-244504 in which capacitor electrodes and loop-shaped inductors formed by combinations of line electrodes and via-electrodes are disposed within a multilayer body including a plurality of insulating layers. In the multilayer band pass filter disclosed in Japanese Unexamined Patent Application Publication No. 2011-244504, a plurality of resonators defined by parallel LC resonance circuits are sequentially coupled with each other.
An LC resonator component is disclosed in Japanese Patent No. 3501327 in which capacitor electrodes disposed parallel with insulating layers and an inductor conductor, one end of which is perpendicularly connected to one of the capacitor electrodes, are disposed within a multilayer body including a plurality of insulating layers.
In the configuration disclosed in Japanese Unexamined Patent Application Publication No. 2011-244504, it is difficult to provide an attenuation pole, as desired, outside of a passband. If the number of reactance elements is increased to provide an attenuation pole, the size of the multilayer band pass filter is increased. In the multilayer band pass filter disclosed in Japanese Unexamined Patent Application Publication No. 2011-244504, although a ground electrode is disposed along the bottom surface of the multilayer body, the multilayer band pass filter, as a whole, does not have a shielding function. If, in the configuration disclosed in Japanese Unexamined Patent Application Publication No. 2011-244504, a ground electrode is formed along the top surface of the multilayer body, an unwanted capacitance is generated between a line electrode and the ground electrode, which may decrease the characteristics of the band pass filter.
In contrast, in the configuration disclosed in Japanese Patent No. 3501327, ground electrodes are disposed along the top and bottom principal surfaces of the multilayer body, and thus, the above-described shielding function can be provided. However, in accordance with a lower height of the multilayer body, the inductance exhibited by a via-electrode is reduced. This makes it impossible to form a resonator having a desired resonant frequency or a filter having desired band pass characteristics. Thus, it is difficult to decrease the size of the LC resonator component.